Permissions might be the culprit here. If the sourcetype configurations are in the user folder, then they don't get exported with the app. If they are in the local folder of a different app, then they won't get exported.
Run this to see where it is on your local Splunk server, and then move it to the app where it needs to be.
$SPLUNK_HOME/bin/splunk cmd btool props list --debug
Look for your source type, it will show you where the config is being pulled from.